1// -*- C++ -*-
2//===----------------------------------------------------------------------===//
3//
4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5// See https://llvm.org/LICENSE.txt for license information.
6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7//
8//===----------------------------------------------------------------------===//
9
10#ifndef _LIBCPP___RANGES_RBEGIN_H
11#define _LIBCPP___RANGES_RBEGIN_H
12
13#include <__concepts/class_or_enum.h>
14#include <__concepts/same_as.h>
15#include <__config>
16#include <__iterator/concepts.h>
17#include <__iterator/readable_traits.h>
18#include <__iterator/reverse_iterator.h>
19#include <__ranges/access.h>
20#include <__type_traits/decay.h>
21#include <__type_traits/is_reference.h>
22#include <__type_traits/remove_cvref.h>
23#include <__type_traits/remove_reference.h>
24#include <__utility/auto_cast.h>
25
26#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
27# pragma GCC system_header
28#endif
29
30_LIBCPP_BEGIN_NAMESPACE_STD
31
32#if _LIBCPP_STD_VER >= 20
33
34// [ranges.access.rbegin]
35
36namespace ranges {
37namespace __rbegin {
38template <class _Tp>
39concept __member_rbegin = __can_borrow<_Tp> && requires(_Tp&& __t) {
40 { _LIBCPP_AUTO_CAST(__t.rbegin()) } -> input_or_output_iterator;
41};
42
43void rbegin() = delete;
44
45template <class _Tp>
46concept __unqualified_rbegin =
47 !__member_rbegin<_Tp> && __can_borrow<_Tp> && __class_or_enum<remove_cvref_t<_Tp>> && requires(_Tp&& __t) {
48 { _LIBCPP_AUTO_CAST(rbegin(__t)) } -> input_or_output_iterator;
49 };
50
51template <class _Tp>
52concept __can_reverse =
53 __can_borrow<_Tp> && !__member_rbegin<_Tp> && !__unqualified_rbegin<_Tp> && requires(_Tp&& __t) {
54 { ranges::begin(__t) } -> same_as<decltype(ranges::end(__t))>;
55 { ranges::begin(__t) } -> bidirectional_iterator;
56 };
57
58struct __fn {
59 template <class _Tp>
60 requires __member_rbegin<_Tp>
61 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
62 noexcept(noexcept(_LIBCPP_AUTO_CAST(__t.rbegin()))) {
63 return _LIBCPP_AUTO_CAST(__t.rbegin());
64 }
65
66 template <class _Tp>
67 requires __unqualified_rbegin<_Tp>
68 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
69 noexcept(noexcept(_LIBCPP_AUTO_CAST(rbegin(__t)))) {
70 return _LIBCPP_AUTO_CAST(rbegin(__t));
71 }
72
73 template <class _Tp>
74 requires __can_reverse<_Tp>
75 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const noexcept(noexcept(ranges::end(__t))) {
76 return std::make_reverse_iterator(ranges::end(__t));
77 }
78
79 void operator()(auto&&) const = delete;
80};
81} // namespace __rbegin
82
83inline namespace __cpo {
84inline constexpr auto rbegin = __rbegin::__fn{};
85} // namespace __cpo
86} // namespace ranges
87
88// [range.access.crbegin]
89
90namespace ranges {
91namespace __crbegin {
92struct __fn {
93 template <class _Tp>
94 requires is_lvalue_reference_v<_Tp&&>
95 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
96 noexcept(noexcept(ranges::rbegin(static_cast<const remove_reference_t<_Tp>&>(__t))))
97 -> decltype(ranges::rbegin(static_cast<const remove_reference_t<_Tp>&>(__t))) {
98 return ranges::rbegin(static_cast<const remove_reference_t<_Tp>&>(__t));
99 }
100
101 template <class _Tp>
102 requires is_rvalue_reference_v<_Tp&&>
103 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t) const
104 noexcept(noexcept(ranges::rbegin(static_cast<const _Tp&&>(__t))))
105 -> decltype(ranges::rbegin(static_cast<const _Tp&&>(__t))) {
106 return ranges::rbegin(static_cast<const _Tp&&>(__t));
107 }
108};
109} // namespace __crbegin
110
111inline namespace __cpo {
112inline constexpr auto crbegin = __crbegin::__fn{};
113} // namespace __cpo
114} // namespace ranges
115
116#endif // _LIBCPP_STD_VER >= 20
117
118_LIBCPP_END_NAMESPACE_STD
119
120#endif // _LIBCPP___RANGES_RBEGIN_H
121